1. Field of the Invention
The present invention is related to hardware structure of processor core as well as multi-core processor, and a method for processing software on such a multi-core processor.
2. Description of the Related Art
For information systems, such as computers and embedded systems, processors including microprocessors, DSPs, micro controllers and so forth continues to improve its performance by, for example, increasing operating clock frequency, density of transistors in line with advancement of semiconductor technologies. Especially, for increasing functionality and processing efficiency, processor cores tend to increase their circuit scale by integrating more transistors into a chip, or a single piece of semiconductor die.
On the other hand, recently other approaches are chosen to improve computing performance than implementing a large scale circuitry into a single piece of the die. One approach is to increase the number of processor cores on a single die for executing parallel processing, or to combine different types of processor cores having respective operation purposes on a single chip. This is because performance improvement will become marginal even when a complexity due to the number of transistors is increased. For example, doubling the die size merely increases the performance only by the square root of two, or about 1.4, as known as Pollack's Law. It results in disadvantages as increase in power consumption as well as generation of heat caused by a more number of transistors, rather than the improvement of a processor core performance therefrom. A processor integrating multiple processor cores is sometimes called a multi-core processor, or a many-core processor.
In technology trends in this field, the multiple processor core approach has been common these days especially in application processors. For example, in application fields such as mobile devices and high performance computing whose performance per power is crucial, multi-core processor has been one of typical approaches. A pre-grant Japanese patent publication, JP 2007-316859 A, which corresponds to a pre-grant US patent publication No. 2007/0,273,699, discloses a computer architecture having multi-core processor. In addition, a concept of GPGPU, General Purpose computations on Graphics Processing unit, is also attracting a great deal of attention. It is because such a concept can provide a general-purpose computation with utilizing highly parallel processing by adopting integer operations and conditional branches instructions on a GPU, Graphics Processing Unit. Generally, these multi-core processors integrating processor cores are made in two styles: in one style called a homogeneous multi-core, identical type of processor cores are integrated, whereas in the other style called a heterogeneous multi-core, different types of processor cores are integrated.